In the past, forehearth outlets have been closed with ceramic rings that were lined with a metal sleeve such as disclosed in U.S. Pat. No. 3,508,904, to Keefer. In this patent a liner was formed of an inverted frusto-conical configuration mounted to cover the inner surface of the orifice ring. Resistance to the erosive and corrosive effect of moving molten glass at elevated temperature is recited as one benefit of the metal liner.
Another U.S. Pat. No. 2,433,116 to Greenbowe et al, discloses a platinum rhodium alloy liner for a continuous flow orifice through which molten glass for forming tubing is flowed. A metal clad, ceramic mandrel extends through the orifice member to serve as the former about which the molten glass flows in the production of glass tubing.
In the instance of U.S. Pat. No. 3,508,904, the metal orifice liner is disclosed as having its upper edge formed with a horizontal ledge that is, in effect, clamped between the upper surface of the orifice ring and the bottom surface of the feeder bowl.
In the Greenbowe et al patent the metal orifice liner or die appears to have its upper rim curled outwardly and downwardly with its outer rim extending into an annular space in the top of the ceramic orifice that is filled with a cement.
It is an object of the present invention to provide a ceramic feeder orifice with a metal insert that is held in the lower opening in the orifice ring
It is a further object of the present invention to provide a metal insert for an orifice ring which is designed to fit loosely in the orifice from a horizontal dimension point of view but is held in the orifice by an annular threaded nut on the lower end of the insert
It is a still further object of the invention to provide a metal insert that fits within the ceramic orifice of a glass feeder with the insert held by a threaded nut on the bottom of the insert where the nut has a specific upper sloping surface that engages the bottom of the orifice ring to firmly hold the insert but not crack the ring on thermal expansion.
Other and further objects will be apparent from the following description taken in conjunction with the annexed sheets of drawings.